This invention relates to an industrial robot equipped with an articulated arm unit.
More particularly, the present invention relates to an industrial robot adapted, for example, to carry out the loading, transfer or its analogous work of heavy items at factories and the like in place of human workers, which industrial robot is capable of memorizing the details of work assigned thereto and performing that work repeatedly by a command to that effect.
The industrial robot according to this invention is of such a type that it is equipped with an articulated arm unit capable of performing complex motions like human arms, and the articulated arm unit is formed of a first arm pivotally supported at its basal end portion, a second arm pivotally coupled with the first arm, a holder case serving as a wrist and pivotally connected to the free end of the second arm and a holder disposed in the holder case in such a way that the holder can turn in a direction perpendicular to the direction of rotation of the holder case. The holder may be provided replaceably with a hand most suitably selected for an item to be handled.
To perform the loading or unloading work of heavy items with such a hand, a great power is required. Thus, electric-hydraulic servo system is used to actuate the hand. The robot is numeric controlled by measuring the extent of each movement of each arm, hand or the like by an encoder or its analogous means so as to perform accurate motions. Accordingly, robots of this type are each provided with a microcomputer as its brain.
It is most common for robots of the above-mentioned type to have them store first of all assigned handling motions in their memories and then actuate them. It is thus indispensable for operators to teach them how their hands should be moved.
Conventional articulated arm units, which made use of gear trains, involved a problem that this teaching work was difficult with them.
For example, they were accompanied by such a drawback that it was impossible to carry out any teaching work requiring a smooth actuation of an arm, since, when a holder coupled with a holder case via a gear train was turned, the holder case also developed an induced motion such as an oscillation motion. To solve the above-mentioned problem of induced motions, it may be contemplated to incorporate a mechanism to perform compensatory motions in the holder case. This however creates another problem that the holder case becomes inevitably large in its external dimensions and, when a hand is attached to the holder case, its handling work is subjected to limitations, particularly, in a narrow place.